This invention relates to integrated optics and, more particularly, to externally controllable miniature lasers and methods of lasing.
Lasers are frequently formed of inactive materials which propagate light and which are doped or otherwise include laser active materials such as dyes or other elements or compounds which are activated or excited when pumped by light of a certain wavelength to produce light at a lasing wavelength. In order to effect lasing in such laser materials, feedback must be created or be present in the material. When feedback exists, the light being emitted by the excited laser molecules will be reflected back upon itself to cause coherent emission from all of the excited molecules and, thereby, cause lasing.
Such laser feedback has been obtained in several ways in the past. In lasers of some size, mirrors have been utilized to create the necessary feedback cavity. Such mirrors may be made, for example, by silvering the ends of an optical wave guide through which the light is propagated. Mirroring has several disadvantages. In the first instance, the ends of the wave guide are frequently incapable of being smoothed to a degree necessary to prevent substantial loss of light due to scattering. In the second instance, mirrored cavities are permanent in nature and other means must be relied upon to effect switching of the laser. Even more significantly, mirrors are generally unusable in integrated optics lasers which employ extremely thin light propagating films of only a few microns in thickness, since mirroring is not easily adapted to the microscopic proportions in the thin films used in integrated optics.
In integrated optics lasers, distributed feedback has generally been achieved in the past either by permanently corrugating the film or by a permanent periodic change in the index of refraction of the thin film. Distributed feedback has been employed in lasers utilizing solid crystal materials or organic films.
Unlike prior lasers, the laser of the present invention has a switchable spatially periodic deformation controlled directly by a force which is impressed on or across the material. The light propagating material of the present invention is preferably formed of a thin elastomer film and this film is preferably deformed by an electric field so as to effect a spatially periodic change in thickness or, more generally, cross-section of the thin film. Such changes in cross-section at properly spaced intervals result in lasing of the light by creating distributed feedback in the film.
In one principal aspect of the present invention, a laser comprises an optical wave guide formed of a deformable material of a given cross-section. The deformable material is capable of guiding light at a predetermined wave length and a laser active material is in the deformable material. Deforming means exerts a force on the deformable material to physically deform the material to cause a change in the given cross-section while the light is being guided through the wave guide to produce laser feedback.
In another principal aspect of the present invention, the deforming means comprises electrode means, and either the electrode means or areas of differing elastic modulus in the deformable material are spaced so as to result in spatial periodic deformation of the deformable material.
In another principal aspect of the present invention, a method of lasing comprises the steps of guiding light through a deformable material of given cross-section having a laser active material therein, and changing the given cross-section to produce laser feedback by physically deforming the deformable material by exerting a force on the material while guiding the light therethrough.
In still another principal aspect of the present invention, the method of lasing includes deforming the material by impressing an electric field across the wave guide so as to spatially periodically deform the material.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.